The state of hydration in humans is a delicate physiological parameter with direct effects on the functional performance at the cellular, organ, and systemic level. Studies have shown that deviations as small as 2% lower than normal levels of hydration (i.e., dehydration) can reduce cognitive and physical performance of a person by more than 30%. Unfortunately, monitoring hydration is neither straightforward nor standard practice; methods include analyzing markers of hydration such as serum ion concentration (invasive), urine color/osmolality, and body mass. Among these, acute changes in body mass and urine color are the most convenient techniques due to their non-invasive nature. However, each of these methods poses shortcomings, including the need for a (non-portable) scale for the mass technique, or the delayed indication of hydration (compared to plasma osmolality) in the urine method. Therefore, improvements are needed in the field.